MIDDLE WARE TECHNOLOGIES

1
MIDDLE WARE TECHNOLOGIES

• B.TECH III YR II SEMESTER
• UNIT 6 PPT SLIDES

TEXT BOOKS
1.Client/Server programming with Java and
CORBA Robert Orfali and Dan Harkey, John Wiley
Sons,SPD 2nd Edition 2. Java programming with
CORBA 3rd Edition, G.Brose, A Vogel and K.Duddy,
Wiley-dreamtech, India John wiley and sons
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INDEX UNIT 6 PPT SLIDES

• S.NO. TOPIC
  LECTURE NO. PPTSLIDES
• 1.CORBA initialization protocol L41
  L1.1 TO L1.4
• 
  L42 L2.1 TOL 2.4
• 
  
• 2.CORBA activation services L43
  L3. 1 TO L3.3
• 
  L44 L4. 1 TO L4.3
• 3. CORBAIDL mapping L45
  L5. 1 TO L5.3
• 4. java-to-IDL mapping . L46
  L6. 1 TO L6.3
• 
  L47 L7. 1 TO L7.3
• 5. The introspective L48
  L8. 1 TO L8.3
• CORBA/Java object L49
  L9. 1 TO L9.4

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UNIT6 SYLLABUS

• Existential CORBA CORBA initialization protocol,
  CORBA activation services, CORBAIDL mapping CORA
  java-to-IDL mapping. The introspective CORGA/Java
  object.

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EXISTENTIAL CORBA

• A new service provider will first register its
  service with the trader and then provide
• An object reference which can be used by
  clients to comment
• The service type name methods, parameters,
  ret-type etc
• The properties the service name value pairs
• The trader maintains a repositiing of service
  types ex restaurant.
• The Trader stores type descriptions in its
  service type repositing.

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EXISTENTIAL CORBA

• Federations Traders groups electronic basers.
• The traders service lets you prove a search via
  policies, constraints and preferences.
• Policies Scope of the search. Ex hop-count to
  limit the no.of trader links traversed.
• Constraints Search criteria language can be
  specified. Ex ltltSQLgt.
• Preferences order in which the matching offers
  are returned.
• Ex first (default), max, min, random, with
  constraint layers- ltltSQLgtgtetc

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EXISTENTIAL CORBA

• Prestarting server objects before clients connect
  to them, is a costly exercise, since there could
  be millions of server objects.
• The server side of the ORB has to provide an
  automatic startup function. The ORB should be
  able to either prestart an object or start it on
  demand, when clients invoke it.
• It must also cooperate with a persistent service
  to save and restore the state of your server
  objects.
• Topics covered ORB activation and deactivation
  policies by BOA Visibroken for java activation
  policies, CORBA 3.0 POA POA-EOB.

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EXISTENTIAL CORBA

• The CORBABOA interfacemethods to create or
  destroy obj.ref., to query or update the infn.
  The BOA maintains for an obj.
• Create, change-implementation, get-id,
  dispose,get-principal,set-exception,
  impl-is-realy,obj-is-ready,deactivate-impl,deactiv
  ate-obj.
• Infn to be supplied a) Interface name b)
  Implementation name 3) Some unique ref data (or
  ID) persistent ID (PID).
• Activation policies CORBA 2.0 defines 4
  activation policies
• a) shared server b) unshared server c)
  server-per-method and d) persistent server
• a) BOA shared server

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EXISTENTIAL CORBA

• BOA activates the server the first time a request
  is invoked on any obj. implemented by that
  server.
• The server initializes itself notifies the BOA
  impl is ready. All subsequent requests are
  then diverted to this process.
• when the process is ready to terminate, it
  notifies BOA deactivation-impl. All the objects
  that are running with in the process are
  deactivated automatically.
• you can also deactivate an individual object, by
  issuing deactivate object.

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EXISTENTIAL CORBA

• Threads are used to run multiple objects
  concurrently with in the process.
• you can even use multiple threads to represent
  the same object to multiple clients serialize
  the access to state (data base) or treat it as a
  Java synchronized method.
• Note make sure your ORB is thread safe
  visibroker for java is thread-safe.

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EXISTENTIAL CORBA

• BOA Unshared server
• Each object in a differ.server process.
• new server activated first time a request is
  invoked the object. It notifies BOA
  object-is-ready.
• A new server object remains active, until
  deactivate object.
• usage dedicated object to represent provides,
  but on a manufacturing line etc.

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EXISTENTIAL CORBA

• c) BOA server-per-method
• New server for each new request.
• Server runs only for the deviation of the
  particular method.
• Several server processes for the same object- or
  even the same method of the same object-may be
  concurrently active.
• No notification to BOA, when an object is
  activate or deactivated.
• Most infrequent usage useful for running
  objects or
• d) BOA Persistant Server

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EXISTENTIAL CORBA

• Servers are activated by means outside BoA.
• impl-is-ready call is used to notify BoA.
• Usage it is just a special case of shared
  server
• Server activation is not by BoA
• DBMS, ODBMS, TPMonitor or web server of all the
  time.
• So there are good candidate apps. For the
  persistent server policy.
• Shared server activation scenario

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EXISTENTIAL CORBA

• The visibroker Activation Daemon
• CORBA 3.0s PoA
• CORBA 2.0 client side portable but nor server
  side resulting in ORB to look after and diff.
  vendors have diff. standards.
• CORBA 3.0 PoA June 1995- implemented is
  Visibroker for Java3.1 orbix web 3.0, and the JDK
  1.2 version of java IDL.
• BoA PoA can consist.
• obj. is ready replaced by connect.
• deactivate-obj replaced by disconnect.

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EXISTENTIAL CORBA

• PoA
• Transparent activations of objects, like BoA.
• Like BoA, PoA can start
• server prog. for each method,
• separate prog. for each object,
• thread prog. for all instances of an obj.type.
• Like BoA, PoA supports both IDL-generates static
  skeletons DSI.
• PoA supports transient or persistent objects.
• New concepts servant mangers call back
  objects, object maps etc.
• Server

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EXISTENTIAL CORBA

• PoA policies
• Policy Type Policy Desc. Choices
• 1. Thread ORB-CTRL-MODEL-ROOT-PoA Default
• SINGLE-THREAD-MODEL.
• 2. Life span TRANSIENT default
• PERSISTENT
• 3. Obj.id uniqueness UNIQUE ID-default
  MULTIPLE ID
• 4. Id.Assignment USER-IDSYSTEM-ID-default
• 5. Servant Retention RETAIN-default NON-RETAIN
• 6. Activation IMPLICIT ACTIVATION-default
  No-
• IMPLICIT ACTIVATION
• 7. Request Processing USE-ACTIVE-OBJECT-MAP-ONLY-
  default,
• USE-DEFAULT-SERVANT
• USE-SERVANT-MANAGER

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EXISTENTIAL CORBA

• Different Policies Combinations
• 1. RETAIN and USE-ACTIVE-OBJECT-MAP-ONLY
• - good for serves that manage finite no.of
  pre-started objects.
• 2. RETAIN and USE SERVANT MANAGER
• - ideal for large no.of persistent objects.
• 3. RETAIN and USE-DEFAULT-SERVANT
• - ideal for situations where one servant is used
  per method call.
• PoA creating object References can be exported
  to clients
• 1. By explicitly invoking the PoAs factory
  methods.
• - Create-reference and create-reference with id
  methods.

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EXISTENTIAL CORBA

• 2. Explicitly at obj. activation
• - activate object and activate-object-with-id
  methods.
• 3. Implicitly at obj.activation policy
  declaration.
• Object Activation
• 1. Explicitly, is a calls to the PoA.
• 2. On-demand, using a servant manager.
• 3. Implicitly policy declaration
• PoA interfaces
• org.omg.CoRBA, servant manager, servant
  activator, servant locator, Adapter Activator.
  PoA interface etc.

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EXISTENTIAL CORBA

• To support multiplatform and Multilanguage world
  of distributed clients and servers, we need
  IDL-to Java mapping.
• The IDL-to-Java language mapping also defines an
  interface for portable stubs and skeletons that
  CoRBA vendors must support.
• The CoRBA IDL to Java Mappings
• CoRBA IDL Java
• General Constructs
• 1. Module Package
• 2. User exceptions java class extends
  org.omg.CoRBA user
• exception, which in twin extends java.long
  exception
• 3. System exceptions Java class
  org.omg.CoRBA.System

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EXISTENTIAL CORBA

• Exception-extends java.long.RuntimeException.
• 4. in parameters normal java parameters
• 5. out and inout parameters Java holder classes
  (IDL generated and then
• instantiated by client side)
• 6. Type casts (or narrow) java helper classes
• 7. Attributes Java overloaded accessor and
  modifier
• methods with the same name as the attribute.

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EXISTENTIAL CORBA

• CoRBA IDL Java
• Primitive Types
• 1. Const Public static final field
• 2. Boolean, TRUE,FALSE Boolean. True. False
• 3. char, wchar char
• 4. octet byte
• 5. string, wstring java.long.string
• 6. short, unsigned short short
• 7. long, unsigned long int
• 8. long long, unsigned long long long
• 9. float float
• 10. double double

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EXISTENTIAL CORBA

• Constructed Types
• 1. interface interface
• 2. sequence array
• 3. array array
• 4. struct java class with same name as struct
  type (includes instances variables and
  constructors for each field)
• 5. enum java class with same name as enum type.
• 6. union java class with same name as union type
  class with get/set methods for fields.
• 7. type def java does not have a type def
  construct. Mapped to simple IDL types or user
  defined IDL types.
• 8. ary java class org.omg.CoRBA.ary (the ORB is
  the factory)

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EXISTENTIAL CORBA

• CoRBA IDL Java
• Server.side Mapp
• 1. Server implementation using write an
  implementation class that extends
• inheritance the IDL-generated-ltinterface-namegtI
  mpl base class.
• 2. Server implementation using IDL-generated
  tie-ltinterface.namegtclass using delegation (i.e,
  Tie) that delegates calls to the implementation

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EXISTENTIAL CORBA

• class you provide. The implementation class
  implements one or more IDL-defined interfaces
  (each represented by an IDL-generated
  ltinterface-namegt operations interface)
• 3. PoA root servant class java class
  org.omg.CoRBA.portable.object
• Impl.pseudo.objects to java classes (only most
  frequently used are tested).

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EXISTENTIAL CORBA

• 1. CoRBAORB Java class org.umg.CoRBA.ORB
• 2. CoRBAObject Java class
  org.umg.CoRBA.Object
• 3. CoRBANamed value Java class
  org.umg.CoRBA.Named value
• 4. CoRBANVList Java class
  org.umg.CoRBA.NVList
• 5. CoRBARequest Java class
  org.umg.CoRBA.Request
• (and DSI mapping)

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EXISTENTIAL CORBA

• 6. CoRBAServer Request(and DII) Java class
  org.umg.CoRBA.server request
• 7. CoRBAType code Java class
  org.umg.CoRBA.Type code
• 8. CoRBATCKind Java class org.umg.CoRBA.TCKin
  d

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EXISTENTIAL CORBA

• Feature CoRBA comp. JavaBeans
• Events
• 1. Add/remove event listeners yes yes
• 2. Event object yes yes
• 3. Event listener yes yes
• 4. Too many listeners yes yes
• (Multicast/Unicast)
• Simple properties
• 5. get/set single value yes yes
• 6. get/set indexed yes yes
• 7. is/set Boolean yes yes

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EXISTENTIAL CORBA

• Bound properties
• 8. Property change event yes yes
• 9. Property change listener yes yes
• 10. Property change support yes yes
• Constrained properties
• 11. Property change Event yes yes
• 12. Vetuable change listener yes yes
• 13. Vetoable change support yes yes
• 14. Property Vector Exception yes yes
• 15. Asynchronous Veta notification yes No

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EXISTENTIAL CORBA

• Customization
• 16. Property editor yes yes
• 17. Customizer yes yes
• 18. HTML help yes yes

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EXISTENTIAL CORBA

• MetaData
• 19. Interface Reposting/IDL yes i/o
• 20. Introspector yes yes
• 21. BeanInfo yes, comp.Info yes
• 22. Feature Descriptor yes yes
• 23. Property Descriptor yes yes
• 24. Method Descriptor yes yes
• (Derived from the CoRBA IRs operation Def)
• 25. Event set Descriptor yes yes
• 26. Vensin Descriptor yes No

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EXISTENTIAL CORBA

• Packaging
• 27. Serialization yes yes
• 28. JARs yes yes
• (Called Component Archive or CAR)

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EXISTENTIAL CORBA

• 29. Manifest yes yes
• 30. Deployment Descriptor yes yes
• 31. Installation Support yes No
• Composition and containment
• 32. Container yes yes, JDK 1.2 Bean
• Context
• 33. Containee yes yes, with JDK 1.2
• 34. Container Listener yes yes, with JDK 1.2
• 35. Multiple Interfaces yes, aggregation yes,
  Beans.getInstance of

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EXISTENTIAL CORBA

• Comp. Life Cycle
• 36. Factories yes yes, with EJB
• 37. Activate/deactivate yes yes, with EJB
• 38. Persistent object refs yes yes, with EJB
• 39. Move yes No
• 40. Remove yes No
• CoRBA Remote Events

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EXISTENTIAL CORBA

• Like JavaBean, CoRBA listeners must implement on
  Event xxx listener that extends the event
  listener interface. Similarly add/remove xxx
  listener.
• Added.adv CoRBA event objs. Can be transmitted
  over the n/w done by pass-by-value semantics.
• Dist.Event channel
• CoRBA Containers Container containee
• Useful for maintaining comp. hierarachy.
• Ability to assemble components inside a
  container.